Whoever is overcome by sleep and he does not wake up until after the rising of the sun should pray fajr just as he used to pray it beforehand, and he prays the Sunnah of the fajr before that.
For indeed it is established that the Messenger of Allaah sal Allaahu alaiyhi wa sallam was overcome by sleep in a journey and neither he nor his Companions woke up until after the rising of the sun.
So the adhaan was called for it (the prayer) and he prayed the optional prayer before ( the obligatory two rak’ahs) then he prayed it (the obligatory two rak’ahs) – salawaat ullaahi wa salaamuhu alaiyhi. (Bukhaari 2/66, Muslim 681)
And with Allaah is the tawfeeq. And may peace and blessings be upon our Prophet Muhammad and his family and his Companions.